1. Field of the Invention
The present invention relates to disinfection systems for wastewater treatment systems, and particularly to a disinfection irradiation of the wastewater with ultraviolet light.
2. Description of Related Art
Many homes in rural and outlying areas are not connected to municipal water systems and rely on septic tank systems, aerobic treatment systems, small package plants or other types of local treatment apparatus (collectively “packaged plants”) for wastewater treatment. These wastewater treatment systems are usually one or more tanks containing the treatment apparatus, connected to a field drip system or drainfield for ultimate disposal of the treated wastewaters. Treatment entails degradation of wastes in the waters by the biological processes of bacteria and micro-organisms. The discharged effluent will generally contain these bacteria and microorganisms.
Effluent quality produced by package plants is usually regulated by one or more governmental agencies. Many agencies require that the discharged wastewaters be disinfected to reduce the potential hazards caused by the presence of bacteria/microbes in the treated effluent. One common type of germicidal or disinfection treatment is chemical treatment with a chlorine type compound. Another common treatment is irradiation with ultraviolet light. It is known that irradiation of water with ultraviolet light within the range from about 150 nanometers through about 300 nanometers is effective in destroying microorganisms. See e.g. U.S. Pat. No. 5,019,256; U.S. Pat. No. 5,256,299; U.S. Pat. No. 5,422,487; or U.S. Pat. No. 5,624,573.
Both of these disinfection treatments require a separate “contact” chamber that is isolated from the wastewater treatment chamber to prevent sterilization or death of the treating bacteria within the treatment chamber (which would disrupt or stop the treating process). In the case of UV treatment, a UV contact chamber can be positioned at various locations within the discharge stream: within the treatment tank or a dosing tank or as a stand alone device between these tanks or after the dosing tank (if present) and prior to the drain field (note, some treatment systems may not include a drainfield). In any event, the owner or operator of the treatment facility must be able to access the contact chamber to service the fixtures, for instance, to replace the UV bulb as necessary. If the contact chamber is located outside a tank, the UV contact chamber must be accessible from the surface, as it will generally be buried in the ground.
One type of UV contact chamber is shown in U.S. Pat. No. 6,296,775, issued to Moody et al., hereby incorporated by reference. That device shows a UV lamp positioned in a “U” shape pipe. Influent enters on one side of the “U” and is treated on the other side of the “U”, where after, the treated waters exit the contact chamber. The Moody device has disadvantages in that the “U” shape created a large foot print for the device, making it more labor intensive to install, either in the ground, or in the treatment tank itself. Further, the Moody device contains an insert for holding the UV lamp having opening to allow waters to pass through to reach the lamp for treatment. While the inlet keeps the UV lamp fixed in place, the openings can become clogged, requiring maintenance.